Production of magnetizable materials



' Patented July 5,1938

PATENT OFFICE PRODUCTION OF MAGNETIZABLE MATERIALS Hans Hiemenz, Hanau-on-the-Main, Germany Application April 2, 1936, Serial No. 72,364

In Germany April 8, 1935 Claims.

grees of cold-molding, for instance, cold-rolling.

E. g. to obtain a high stability one has proposed to provide a. double cold-molding with interme-' diary annealing between thecold-molding steps, relatively large reductions of the cross-section being accomplished in both cold-molding steps.

It is true that a satisfactory stability of the permeability is obtained in this way, but not yet suf- .ficiently high values of the permeability, as, for

instance, required for the cores of Pupin coils which are to have as small a volume as possible, or for the continuous loading of cables. .Finally for materials used in the teletransmission industry not only their qualities as to permeability are important, but on the other hand their hysteresis 2 number, i. e. the resistance loss caused by hysteresis must be as small as possible. The hysteresis number is usually measured'in ohms per henry and per ampere-winding/cm. at 800 Hertz.

A minimum value of the hysteresis number is I desirable inorder to reduce to a minimum the so called quality number, i. e. the quotient of the hysteresis number divided by. the square root of the permeability. According to the present invention the combi- A nation of high permeability, high constancy and stability of the permeability and small hysteresis number is obtained by dividing the cold molding into two steps in such a manner that the strip a or wire is brought to 20-100 times its original length in the first operation and the product of this operation to 1.06-1.35. times its length in the second operation.

The temperature and the duration of the an nealing operation between the two cold-molding steps depend upon the composition of the material used.v As an approximation it may be stated that the temperatures will lie within thelimits of 900 to 1200 C., the preferred temperature being 1100 C. -The duration of the annealing operation pref erably amounts to no more than '30 minutes and may even be less than one minute. In the most cases it is recommendable to cool down the material from the annealing temperature rapidly, for =-i-nstance, by passing the strip to be heated through an annealing furnace or by quenching it in water.

be added to the material to be treated.

- By the above described treatment permeability values of from to 130 are obtained, the stability and constancy of the permeability being quite satisfactory.

The double cold-molding may be combined with 5 rolling the material down to a thickness at which the permeability in its dependency on the thickness of the strip or wire has already passed the minimum. For explanation it may be added, that when starting from a thickness of a strip or a 10 sheet of 0.5 mm. for instance, the initial permeability decreases with'decreasing thickness, passes a minimum and finally increases when the strips or sheets have become very thin, for example thinner than 0.05 or 0.03 mm. i

To increase the resistance of the products, from 0.1 to 16% of suitable elements such as cop?- per, manganese, titanium, aluminum, chromium, tungsten, molybdenum, vanadium, silicon may 20 The annexed drawing shows how the permea 'bility u and the hysteresis number h depend from the extent .of the second cold-molding operation in the case of an alloy of 50% iron and 50% nickel. It appears from thisdiagram that really on lengthening the strip or wire within the range of about 1.35 times at most the initial length ex-. tremely high'values of permeability are obtained whereas on further lengthening the values of permeability continuously decrease.v The third curve 30 finally shows the values of the quality number 2: l '\/I- It appears that this value which shouldbe as 35 small as possible is yet satisfactory within the range indicatedfor the second cold-lengthening, irispite oi? the high values of permeability. The course of the i, h and I curves in dependency on the lengthening durin the second cold-molding operation varies to a stable permeability, especially with high absolute 50 values ofthe permeability, in the range of weak magnetic fields, which method consists in firstly cold-molding the magnetic material, which is, as usual in the art of coldmolding, in a cast, hotrolled or annealed condition, to about 20 to 55 times its initial length, then annealing the material at a temperature exceeding 900 C. and finally cold-molding the same to 1.06 to 1.35 times its length.

- 2. The method of producing magnetizable materials consisting 01' nickel 35 to 60 parts besides iron 65 to 40 parts and having a constant and stable permeability, especially with high absolute values of the,permeability, in the range of weak magnetic fields, which is, as usual in the art of cold ,molding, in a cast, hot-rolled or annealed condition, which methodv consists in firstly coldmolding the magnetic material to about to 100 times its initial length, then annealing the material at temperatures between about 900 and 1200 C. for a period not exceedingthirty minutes, and

finally cold-molding the same to 1.06 to 1.35 times I its length.

3. The method of producing netiz'able materials cohslsting oi. nickel to 6 parts besides iron 65 to parts and having a constant and stable permeability, especially with high absolute values oi the permeability, in the range of weak magnetic fields, which method consists in firstly cold-molding the magnetic material, which is, as

usual in the art of cold molding, in a cast, hotrolled or annealed condition, to about 20 to,100 times its initial length, then annealing the material at a temperature exceeding 900 C., then rap- 30 idly cooling down the material and finally coldmolding the same to 1.06 to 1.35 times its length.

4. The method of producing magnetizable materials consisting oi nickel'35 to parts besides iron to 40 parts and having a constant and stable permeability, especially with high absolute values of the permeability, in the range of weak magnetic fields, which method consists in firstly cold-molding the magnetic material, which is, as usual in thart oi cold molding, in a cast, hot-rolled or annealed condition, to about 20 to times its initial length, then annealing the material for a period not exceeding one minute at a temperature exceeding 900 C., then rapidly cooling down the materiaband finally cold-molding the same to 1.06 to 1.35 times its length.

5. The method of producing magnetizable'materials consisting of nickel 35 to 60 parts besides iron 65 to 40 parts and having a constant and stable permeability, especially with high absolute 'values of the permeability, in the range of weak magnetic fields which method cons ts in firstly cold-molding the magnetic materia which is, as usual in the art 01 cold molding, in a cast, hotrolled or annealed condition, to about 20 to 100 times its initial length, then annealing the material at a temperature exceeding 900 C., then rapidly cooling down the material by passing it through an annealing furnace, and finally cold- 'moldlng the same to 1.06 to 1.35 times its length. 1 HANS HIEMENZ. 

